DESCRIPTION (verbatim from the proposal): Fibrous encapsulation is an important limitation of current biomaterials intended for integration with soft collagenous tissues (e.g. abdominal wall repair, hernia repair, skin replacement from burn or ulceration, intestinal ulcer repair). A fibrous capsule can wall off the device, produce scar tissue that can adhere to underlying structures, and isolate the material from mechanical or chemical integration. However, preliminary implantation data suggest that if polymer fibers that make up the implant are very small, on the order of collagen fiber dimensions in the soft tissues (0.5-3.0 mm diameter), then fibrous encapsulation is minimized or eliminated. This feature, if validated in a systematic scientific manner, could be utilized in fibro-porous biomaterial design to create more effective devices. A systematic evaluation of a design feature's influence on bio-response (e.g. fiber diameter effect on healing) will be most useful to the biomaterials design community if it is simultaneously compared with a characteristic that has been well-studied. Biomaterial surface chemistry is the feature of interest selected for comparison here. The purpose of this research is to systematically evaluate the influence of material architecture and surface chemistry on in vivo response to fibro-porous materials. The specific aspect of surface chemistry to be evaluated is surface (ionic) electrical charge. The research proceeds in two stages: analysis on single fibers, and analysis on multi-fiber (fibro-porous) meshes. This two-stage approach helps to isolate effects of the different features of interest. Because no traditional biomaterials fabrication method exists for making very small diameter fibers, a technology used mainly in non-biomedical industries called electrospinning is pursued and applied. An in vivo model is used to evaluate fibrous capsule thickness as well as foreign body giant cell density and macrophase cell density in tissue adjacent to the micro-fibers. These are key indicators of implant integration or activation of the foreign body reaction. The significance of this research is to apply an innovative material and fabrication method to assess the influence of specific biomaterial architectural and chemical features of a biomaterial to the tissue response. The approach could lead to a new materials fabrication technology to treat a number of soft-tissue complication in which scar tissue formation is an important clinical problem. The health relatedness of this project is to improve the health and function of persons with soft tissue defects, particularly abdominal wall perforation, intestinal ulceration, abdominal herniation, burns and skin ulceration, i.e. soft-tissue complications that require surgical repair through use of a biomaterial. The new materials will prevent scar tissue formation and reduce the occurrence of secondary complications.